The road to good health is paved with good intestines. That’s not just a clever turn of phrase, it’s actually true. Our gastrointestinal (GI) tract is a virtual ecosystem of bacteria, both good and bad—an amazing 400 species of bacteria and one hundred trillion individual microorganisms, to be exact. Ideally, the ratio of the friendly to unfriendly kinds should be 85 percent to 15 percent.

Probiotics (healthy bacteria found in some foods, as well as supplements) can help promote that balance. A look at some of the important roles beneficial bacteria play explains why that can be so helpful:

Probiotics fuel a healthy bowel. One of the primary roles of probiotics is to digest some types of fiber and produce small fat molecules as a byproduct. These fats (short-chain fatty acids) are a primary source of fuel energy to the cells that line the bowel.

They help you stay well-nourished. They form a barrier on your intestine’s lining against pathogens and toxins while still allowing all the goodness that’s in the food you eat to pass through and be absorbed by your body. Without this, bad bacteria can set up shop, keeping nutrients out and irritating the lining enough that toxins and other enemies can enter your bloodstream.

They may shield you from discomfort. Once levels of good bacteria dip, the harmful type that can take over can give off their own toxins. This can cause GI issues like bloating and constipation, as well as concerns not at all related to your GI tract, such as eczema, fatigue and joint pain. Some research indicates that some cases of irritable bowel syndrome may be caused by an overgrowth of bad bacteria.

Probiotics can help keep your immune system healthy… The most effective immune system, of which the gut is a major part, is one that’s kept quiet until it’s truly needed to spring into action. The latest research on probiotics indicates that they balance this important defense and decrease inflammation, a powerful force that can keep your body unnecessarily on high-alert (as well as contribute to a variety of health issues).

… helping you fend off disease. Good bacteria can actually “talk” to each other and your immune system. In doing so, they can turn on disease-fighting genes or help suppress those that can cause us health troubles. For example, having a preponderance of good bacteria may help battle harmful microorganisms and prevent genetic mutations that cause colon cancer.

Do I Need More Probiotics?

Chances are, the answer is yes. Most people—even those consuming healthy diets—simply don’t get enough on their own and can benefit from getting more (particularly if they have any inflammation). Though there are urine and stool tests that can check your balance of bacteria, your doctor or nutritionist may recommend probiotics for you without ordering them; these tests are costly and typically not covered by insurance.

It’s generally safe to try increasing probiotics in your diet on your own, too. There are hundreds of types of probiotics, but the most common ones are lactobacillus and bifidobacterium. You can find one or both of these in fermented dairy products like kefir, yogurt and soft cheeses (look on the label for these specific names), kombucha (a fermented tea), kim chi, miso, raw sauerkraut and tempeh. Try including at least one in your diet on a daily basis. “The bacteria need to be re-introduced regularly,” notes Lisa Powell, M.S., R.D.N., director of nutrition at Canyon Ranch in Tucson.

Another way to boost your levels of good bacteria is to eat foods that contain prebiotics—a type of carbohydrate that your good bacteria like to feed on for fuel. These are specifically found in the fiber of plant foods. Asparagus, bananas, carrots, chicory, leeks, Jerusalem artichokes, most fruits, onions, shitake mushrooms, tomatoes and turmeric (the spice in curry) are great sources.

Supplements can help bridge the gap most people’s diets will often still leave after making these changes. A broad-spectrum probiotic with 10 to 12 different species of bacteria is best, as is one with colony-forming units (CFUs) in the billions. Recommendations vary depending on your health status, so talk to an integrative physician or nutritionist about which brands, strains and doses may be best for you.

Supplements are particularly useful while and after you take antibiotics, as they can help replace killed-off good bacteria and reduce the risk of antibiotic-related diarrhea. To make sure your supplement’s most effective, be sure to take it at different time than your medication each day. Continue the probiotic supplements for two months after finishing your course, or per your doctor’s recommendation.

“Most probiotics need to be refrigerated to keep bacteria from killing each other off, so be sure to check the label of the brand you’re using.”

Tula Karras is a freelance editor and award-winning writer who covers health, nutrition, fitness, and psychology for print and online outlets. She has held editorial staff positions at WebMD.com, Child, Parents, Seventeen and SELF and is based in Brooklyn, New York.